AIRWAY HYPERRESPONSIVENESS TO HISTAMINE IN MYCOPLASMAL INFECTION - ROLE OF HISTAMINE N-METHYLTRANSFERASE

To elucidate the modulatory role of histamine-degrading enzymes in air way constrictor responses in mycoplasmal infection, we studied hamster tracheal segments under isometric conditions in vitro. Nasal inoculat ion with Mycoplasma pneumoniae potentiated the contractile responses t o histamine but not to methacholine. Pretreatment of tissues with the histamine N-methyltransferase inhibitor SKF 91488 abolished the infect ion-induced potentiation, whereas, the diamine oxidase inhibitor amino guanidine had no effect. The histamine N-methyltransferase but not dia mine oxidase activity in tracheal tissues was decreased in infected an imals. These results suggest that M. pneumoniae causes airway hyperres ponsiveness to histamine probably through a reduction of endogenous hi stamine N-methyltransferase activity. (C) 1998 Elsevier Science B.V.